Field of the Invention
The present invention relates to a semiconductor device and a manufacturing method thereof, and particularly to a semiconductor device having a vertical MOSFET with a trench gate, and a manufacturing method thereof.
Description of the Related Art
There has been known, as one of vertical MOSFETs, one having a structure with a trench gate, in which a gate electrode is embedded into a trench formed in a substrate to make a current flow in a vertical direction. As a method of electrically connecting such a gate electrode lying inside the trench to a gate pad via a gate metal wiring, there has been proposed in, for example, Japanese Patent Application Laid-Open No. 2014-72412, a configuration in which a gate contact hole penetrating an interlayer insulating film on a trench is formed directly on the trench. Thus, the gate electrode can be connected to the gate metal wiring without providing the gate electrode on a gate insulating film at an upper corner portion of the trench, whose breakdown voltage for insulation is low, thereby enabling an improvement in reliability against the breakdown of the gate insulating film and an improvement in transistor performance by a reduction in gate resistance.